catstodon/app/lib/emoji_formatter.rb

# frozen_string_literal: true

class EmojiFormatter
  include RoutingHelper

  DISALLOWED_BOUNDING_REGEX = /[[:alnum:]:]/.freeze

  attr_reader :html, :custom_emojis, :options

  # @param [ActiveSupport::SafeBuffer] html
  # @param [Array<CustomEmoji>] custom_emojis
  # @param [Hash] options
  # @option options [Boolean] :animate
  def initialize(html, custom_emojis, options = {})
    raise ArgumentError unless html.html_safe?

    @html = html
    @custom_emojis = custom_emojis
    @options = options
  end

  def to_s
    return html if custom_emojis.empty? || html.blank?

    i                     = -1
    tag_open_index        = nil
    inside_shortname      = false
    shortname_start_index = -1
    invisible_depth       = 0
    last_index            = 0
    result                = ''.dup

    while i + 1 < html.size
      i += 1

      if invisible_depth.zero? && inside_shortname && html[i] == ':'
        inside_shortname = false
        shortcode = html[shortname_start_index + 1..i - 1]
        char_after = html[i + 1]

        next unless (char_after.nil? || !DISALLOWED_BOUNDING_REGEX.match?(char_after)) && (emoji = emoji_map[shortcode])

        result << html[last_index..shortname_start_index - 1] if shortname_start_index.positive?
        result << image_for_emoji(shortcode, emoji)
        last_index = i + 1
      elsif tag_open_index && html[i] == '>'
        tag = html[tag_open_index..i]
        tag_open_index = nil

        if invisible_depth.positive?
          invisible_depth += count_tag_nesting(tag)
        elsif tag == '<span class="invisible">'
          invisible_depth = 1
        end
      elsif html[i] == '<'
        tag_open_index = i
        inside_shortname = false
      elsif !tag_open_index && html[i] == ':' && (i.zero? || !DISALLOWED_BOUNDING_REGEX.match?(html[i - 1]))
        inside_shortname = true
        shortname_start_index = i
      end
    end

    result << html[last_index..-1]

    result.html_safe # rubocop:disable Rails/OutputSafety
  end

  private

  def emoji_map
    @emoji_map ||= custom_emojis.each_with_object({}) { |e, h| h[e.shortcode] = [full_asset_url(e.image.url), full_asset_url(e.image.url(:static))] }
  end

  def count_tag_nesting(tag)
    if tag[1] == '/'
      -1
    elsif tag[-2] == '/'
      0
    else
      1
    end
  end

  def image_for_emoji(shortcode, emoji)
    original_url, static_url = emoji

    if animate?
      image_tag(original_url, draggable: false, class: 'emojione', alt: ":#{shortcode}:", title: ":#{shortcode}:")
    else
      image_tag(original_url, draggable: false, class: 'emojione custom-emoji', alt: ":#{shortcode}:", title: ":#{shortcode}:", data: { original: original_url, static: static_url })
    end
  end

  def animate?
    @options[:animate]
  end
end